A Little Lift
Gliders so responsive they can stay up on a breath of fresh air.
- By Paul Ciotti
- Air & Space magazine, May 2005
(Page 2 of 3)
Dynamic soaring is not a new idea—“It’s been postulated for over a hundred years,” says Osoba—though it’s gained some exposure in recent years through the exploits of hobbyists who pilot radio-controlled model sailplanes. By flying these gliders in oval patterns between the high winds just above a hill and the still air just behind it, they have been able to turn their sedate models—which normally fly at 25 to 40 mph—into screaming rockets that rip around at up to 230 mph, sometimes tearing their wings off in the process.
Seabirds have been dynamically soaring for untold eons. For example, albatrosses take off from the ocean’s surface (with a lot of vigorous flapping and running on water with webbed feet), climb to a height of perhaps 30 feet, lock their wings, and thereafter soar back and forth between the near-stationary air near sea level and faster moving air higher up. Each time they rise into the fast moving air, they get a small energy boost that enables them, as they glide back down into the near stationary air, to travel hundreds of miles a day without flapping their wings.
Although staying aloft with dynamic soaring requires considerable technique, its basic maneuvers are simple enough: When encountering a gust of air, the pilot, instead of fighting to stay level, instantaneously banks to expose his sailplane’s broadest surfaces to the wind and gain a push. Taras Kiceniuk explains it this way: If a sailplane is hit by a sideways gust, the pilot will immediately bank away from the gust, expose the belly and the bottom of the wings to it, and pull a couple of Gs. As the pilot finishes the maneuver and the sailplane’s tail slips parallel to the wind, the downwash from the wings slows the gust, thus reducing the gust’s energy while transferring that energy to the sailplane in the form of higher speed.
When the Carbon Dragon first appeared in the late 1980s, its balsa wood construction and dope-coated wings gave it the appearance of an oversize stick-and-paper model. But Gary Osoba, who started entering it in soaring contests in 1994, proved it was no toy; the sailplane could climb three to four times faster in thermals than other sailplanes and beat them on distance by margins of two to one. The Carbon Dragon could also get aloft two hours before other sailplanes could, and remain there much longer—usually until the sun went down or until, after seven, eight, or nine hours, the pilot had to relieve the pressure in his bladder.
Though Maupin’s team finished the prototype in 1987, downturns in Maupin’s health kept the craft grounded for most of the next six years. It spent just 10 hours aloft during that period, mostly gliding gingerly back to Earth from late afternoon car tows to a mere 300 feet. In 1989 Osoba saw photos of the sailplane in Soaring magazine and called Maupin to ask if he could buy it. For several years, Maupin declined (Osoba had no interest in building his own Carbon Dragon from the plans Maupin was selling), but in the summer of 1993 he relented and sold the prototype.
Osoba’s first flight was a revelation. On an overcast afternoon with weak thermals, he realized how different this sailplane was. “I remember taking off and looking over to the right of the grass strip and seeing a red-tailed hawk sitting on a phone pole,” he says. In the Carbon Dragon, he could stay up when even the hawks weren’t flying. What’s more, he’s since found that takeoff rolls can be as short as five feet—even shorter if the wind is blowing strongly enough. All he has to do then is wait for a gust and pull back on the stick. In the right winds he has been able to settle the glider on the ground vertically, and on occasion land while drifting backward.
But by themselves, mere random gusts aren’t enough to keep a micro-lift sailplane in the air. Micro-lift also comprises what Osoba has termed micro-strings—“thin, string-like animals that flow into thermals like a winding stream would [flow into] a lake.” No more than a wingspan wide, these miles-long horizontal rivers of air can follow erratic paths and make abrupt turns. This is where the slow-flying Carbon Dragon really excels.
When he finds a micro-string, Osoba immediately slips gently into it until his one wing is completely inside. “You can rapidly roll into it and create 2 Gs on that wing relative to the other wing,” he says. “Now it’s not sustainable because you’re not going to do a barrel roll…. What you do then is you roll back out of [the micro-string] at a more gentle rate into the relative sink and reaccelerate, and then you come back and you roll in and out, in and out of the edge of this shearing event, feeling your way along it.” By continually slipping between the different air masses—essentially doing in a horizontal plane the same thing an albatross does in a vertical one—Osoba has been able to fly into the wind for as long as 20 minutes without losing altitude, and at times even gaining some. Osoba will even avoid looking at the ground or clouds for fear they will subconsciously influence his direction. At other times, he flies with his eyes closed to better sense the air. (“Jim Maupin never envisioned the Carbon Dragon being used in this way,” he says. “[Dynamic soaring] arose after we started exploring with it.”)